The present invention relates generally to methods and devices for rapid analysis and determination of composition of multi-component solutions by means of optical monitoring and evaluating the patterns formed during the process of drying of at least one droplet of such solution. More particularly, the invention discloses simple, rapid and sensitive devices for a technique named Droplet MicroChromatography (DMC) designed for assessing various fluids by analyzing the dynamics of sediment pattern formation during the drying of a fluid microdroplet (0.2-10.0 microliter). The proposed approach has a number of unique advantages and in particular it obviates the expense associated with complex proteomic and metabolomic techniques for disease detection which are based on obtaining molecular profiles of bodily fluids.
For the purposes of this description, the word “solution” is used to describe a liquid, which is a product of an act or process by which a solute (whether solid, liquid, or gaseous) is absorbed into and dissolved by a solvent liquid. The solute can be generally regained from the solution by evaporation or drying of a solvent. Suspensions and emulsions are also included in the general category of solutions.
A sub-set of solutions, which is of particular interest for the purposes of the invention, is a category encompassing biological fluids. The term “biological fluid” includes but not limited to the following examples of bodily fluids from animals or humans: blood and blood products such as serum or plasma, saliva, urine, nipple aspirants, synovial fluids, cerebrospinal fluids, sweat, fecal matter, bile, tears, bronchial lavage, swabbings, needle aspirants, semen, vaginal fluids, pre-ejaculate, etc.
The methods of analysis of a solution using the pattern formed by a dried droplet has been known in the prior art for a long time. Initial observations on the potential diagnostic information contained in the patterns formed by dried biological fluids were made over 30 years ago. At the end of the 1960's, the relationship between hormonal changes during the female menstrual cycle and the crystallization of saliva was discovered. Formation of a unique pattern called ferning by a dried droplet of saliva correlates with the fertile period and is related to ovarian function and endocrine activity. Later studies have shown that salivary progesterone concentrations in samples collected by women daily, over extended periods of time, can serve as a means of assessing ovarian function. Based on clinical evidence on the efficacy of detecting a woman's fertile periods by observing characteristic ferning patterns in dried saliva, several US patents were issued on simple optical devices for determining fertile periods. The U.S. Pat. Nos. 4,815,835 by Corona and 5,572,370 by Cho are typical examples of such devices. OvuLook, LLC, a division of TCI Optics, Inc., has developed a commercial device called OvuLook™ and in December of 2001 received FDA clearance for an estrogen based saliva tester that reads ferning patterns.
One of the first attempts to use information contained in the patterns formed by dried biological fluids is presented in the U.S. Pat. No. 4,847,206 issued in 1989 and entitled “Method for the crystal morphological analysis of blood and urine, for early diagnosis and for the production of medicaments”. Examples of dried blood patterns corresponding to certain diseases are described, according to experimental data presented in that patent. The samples used for obtaining the patterns shown in that US Patent require a complex and long preparation procedure, which includes many steps such as diluting blood or urine by water, distilling it, calcining the dry cake by heating at a constant rate for a period of 60 to 70 minutes to a temperature of about 600° C., cooling the calcinate for about 2 to 4 hours to a temperature of about 150° C., and several other steps, which altogether make the proposed method hardly practical.
Yakhno et al. conducted extensive studies of various medical and non-medical applications of the drying droplet approach. Results of their studies are summarized in the PCT application No. WO 02/059595 incorporated herein by reference in its entirety and other publications. The major focus on their studies was not the analysis of formed patterns but measurements of “acousto-mechanical impedance” (AMI) of the oscillating quartz on which the droplet of a tested liquid was drying. Several applications of the method were explored, such as quality control of beverages and liquid foods, detection of odors by measuring solutions through which “scented” air was bubbled, and medical diagnostics based on measurements of temporal changes of AMI in the course of drying of a droplet of biological fluids: blood plasma, urine and saliva.
Yakhno reported various potential diagnostic applications of acoustical monitoring of the droplet drying process. It was demonstrated that the drying dynamics of a droplet of blood plasma from a pregnant woman with normal pregnancy differs significantly from that of women at risk for spontaneous abortion. It was also shown that the dynamics of blood serum droplet drying is different for patients with breast cancer and healthy women. The patterns for cancer patients have distinct characteristic features different from those for healthy women, such as larger structural elements and well-defined linear formations. Difference in the patterns for two types of cancer is also quite obvious. Pregnancy results in characteristic patterns. Moreover, there is a clear difference in the patterns for the in-time versus pre-term delivery.
Another example of using the patterns formed by the dried biological fluid droplet is described in the Russian Patents No. 2,127,430 by Buzoverja et al and 2,007,716 by Shabalin et al. The sample of fluid is dried and then the so-called “crystallogram” or pattern is analyzed for the presence of pathological markers.
A general process of determining the biological state through discovery and analysis of hidden biological data is described in the US Patent Application No. 2003/0004402 by Hitt et al. incorporated herein by reference in its entirety. The methods described in this patent application concern processing large volumes of data related to a biological fluid. This patent indirectly provides some useful background information for some aspects of the method of the present invention. More specifically, the use of databases for comparison with the patient's sample as well as neural network based learning systems are described in the patent and may be used for some aspects of the method of the present invention.
This and other methods have a disadvantage of having only the final pattern of the dried droplet available for analysis. There is no mentioning in the prior art of analyzing the temporal and spatial dynamics of structural changes in the sequence of patterns formed by the sediment in the drying droplet although the multitude and sequence of patterns formed and the time intervals between formation of certain patterns can yield substantial information about the composition of the solution.
The need therefore exists for such methods and devices that allow the optical monitoring and analysis of the composition of a solution based on the dynamics of drying of a droplet of such solution.